1. Field of the Invention
The present invention relates to exhaust apparatus, especially such apparatus for use in the cast house of a blast furnace, the apparatus including at least one movable exhaust hood and ducting connected thereto. The invention also relates to a cast house having such apparatus.
2. Description of the Prior Art
Considerable dust nuisance is generated when a blast furnace is tapped. This dust consists mainly of finely divided iron oxide, of which about 70% has a particle size of less than 0.01 mm. More than half the dust formed originates from the point at which the blast furnace is tapped, the rest of the dust coming in approximately equal amounts from the point at which the iron and slag are separated and the point at which the iron is tipped into a transfer ladle or other means of transport.
This dust problem is generally tackled by placing exhaust hoods above the critical points mentioned above. To be efficient, such exhaust hoods have to be of considerable size, and the exhaust ducts connected to them must also be generously dimensioned. As a result, the exhaust apparatus is a considerable hindrance to the personnel operating the blast furnace and the runner system. Various proposals have been made for reducing this hindrance to a minimum. It should, however, be borne in mind that in most existing blast furnaces the space around the furnace is limited and, moreover, that this area has to be kept reasonably clear for work involving clay guns, taphole drills and various transport systems.
For these reasons the idea of making the exhaust hood and the adjoining section of the exhaust duct mobile has already been put forward. Possible ways of achieving this movement are (i) lifting the hood with a crane and moving it, (ii) shortening or lengthening the first part of the exhaust duct telescopically, and (iii) swivelling the duct and the hood. Swivelling arrangements are known in which the considerable weight of the exhaust hood and duct is taken by a crane track or a swivelling crane of fork design which grips the hood or by a heavy pillar running through the cast house which can also act as the exhaust duct. All these proposals for swivelling arrangements, have the distinct disadvantages that they still take up a lot of room, are expensive and above all are difficult to swivel.